Knowledge Bank

A relative transmission attachment is described for automatically recording spectra from 210 to $2700\mu$ using a Beckman Model DU quartz spectrophotometer. The attachment requires the use of only one rotating mirror, detector, amplifier, and commutator along with two tuned rectifiers. The ratio of sample to reference beam intensities is traced on a high-speed recorder. A slit servo operated from the reference signal maintains a reasonably constant reference signal. Representative curves showing the performance of the instrument are reproduced. The applications of differential recording are discussed.